Conventionally, microfabrication has been carried out by lithography using a photoresist composition in the production of semiconductor devices. The microfabrication is a method for processing including forming a thin film of a photoresist composition on a substrate to be processed such as a silicon wafer, irradiating the thin film with active light such as ultraviolet rays through a mask pattern in which a pattern of a semiconductor device is depicted, developing the pattern, and etching the substrate to be processed such as a silicon wafer by using the obtained photoresist pattern as a protection film. In recent years, however, semiconductor devices have been further integrated, and the active light to be used has had a shorter wavelength from a KrF excimer laser (248 nm) to an ArF excimer laser (193 nm). This raises serious problems of the effects of diffused reflection of active light from the substrate and standing wave. Consequently, a method for providing a bottom anti-reflective coating (BARC) between a photoresist and a substrate to be processed has been widely applied. In order to achieve further microfabrication, a lithography technique using extreme ultraviolet rays (EUV, wavelength 13.5 nm) and electron beams (EB) as the active light. In the EUV lithography or the EB lithography, a specific anti-reflective coating is not required because the diffused reflection from the substrate and the standing wave are not usually generated. The resist underlayer film, however, has begun to be widely studied as an auxiliary film for improving the resolution of a resist pattern and adhesion.
On the other hand, as the finer resist pattern formation has been progressed, thinner film formation of the resist has been indispensable. This is because deterioration in resolution is caused by the finer pattern formation and the formed resist pattern is easily collapsed. Consequently, the resist pattern thickness required for substrate processing is difficult to retain. As a result, not only the resist pattern but also the resist underlayer film formed between the resist and the semiconductor substrate to be processed are required to have the function as a mask. In order to form the resist film having a thinner film thickness as described above, a lithography process is used in which at least two layers of resist underlayer films are formed and the resist underlayer films are used as an etching mask. For such a thin film resist, a process of transferring a resist pattern to the underlayer film of the resist by an etching process; and processing a substrate using the underlayer film as a mask, or a process of transferring a resist pattern to the underlayer film of the resist by an etching process; further transferring the transferred pattern of the underlayer film to the underlayer film of the patterned underlayer film using a different etching gas; repeating these processes; and finally processing the substrate is used. The resist underlayer film for the lithography process is required to have high etching resistance to the etching gas (for example, fluorocarbons) in a dry etching process and the like.
As the polymer for the resist underlayer film, the following polymers are exemplified.
A resist underlayer film-forming composition including polyvinyl carbazole is exemplified (refer to Patent Document 1, Patent Document 2, and Patent Document 3).
A resist underlayer film-forming composition using a fluorene phenol novolac resin is disclosed (for example, refer to Patent Document 4).
A resist underlayer film-forming composition including a fluorenenaphthol novolac resin is disclosed (for example, refer to Patent Document 5).
A resist underlayer film-forming composition containing a resin made of fluorenephenol and arylalkylene as repeating units is disclosed (for example, refer to Patent Document 6 and Patent Document 7).
A resist underlayer film-forming composition including carbazole novolac is disclosed (for example, refer to Patent Document 8).
A resist underlayer film-forming composition including polynuclear phenol novolac is disclosed (for example, refer to Patent Document 9).